This invention relates to latches and locks and has particular, but not exclusive, application to door latches which can be released by electrical signals. More specifically, the invention has particular application to catch mechanisms of the general type described in our co-pending Australian patent application No. 73086/74.
Our aforesaid patent application describes a catch mechanism which is designed to be installed in a door frame to cooperate with a conventional door lock and which includes a catch member which can be moved between an operative position in which it can serve the normal catch function and an inoperative position in which to enable release of the door no matter what the condition of the door lock. Such catch mechanisms have particular applications to fire doors and the present invention provides a modified mechanism which will ensure that the door will remain locked in the event of a fire generating very high temperatures.